a) Field of the Disclosure
The present invention relates to a method for processing ethanolamine-containing wastewater generated in a nuclear power plant or thermal power station. More particularly, this invention relates to an advanced treatment method of ethanolamine-containing wastewater, based on a combination of physicochemical and biological treatment processes, which is comprised of the regeneration of cation exchange resin capturing ethanolamine discharged from a nuclear power plant or a thermal power station with sodium hydroxide, the concentration of the regeneration wastewater by evaporation and condensation, and then the treatment of the highly concentrated ethanolamine-containing wastewater through biological decomposition and denitrification processes.
b) Background Art
Nuclear power plants and thermal power stations use water as energy transfer medium to obtain electric energy from nuclear or fossil fuels. Generally, water/steam circulation systems in the plants vaporize water to rotate a turbine that produces electricity, and then condense the vapor to water, continually repeating this circulation.
The circulated and condensed water may corrode parts included in the system. To prevent corrosion, chemicals, such as a pH control agent and a chemical-potential control agent, are injected into the circulating water, thereby controlling electrochemical corrosion of the metal parts of the system.
The water/steam circulation system of the nuclear power plant and thermal power station is installed with an ion-exchange resin tower. Chemicals that are injected into the system to control corrosion are removed, along with some impurities as well, while water remains in the water/steam circulation system. After this step, the chemicals must be injected into the system again. That is, at each water/steam circulation cycle, the chemicals are removed by an ion exchange resin, and then chemicals are newly injected into the system. Such a process is repeated. All chemical species captured by the ion exchange resin are released into the wastewater through a resin regeneration process. This wastewater must meet the environmental discharge standard.
The environmental discharge standard for the wastewater was strict. Since chemicals injected into the system are volatile, they were discharged into the air while the wastewater was treated. For example, heavy metals, etc., discharged from the nuclear plants were treated through a simple physicochemical process.
However, it is difficult to meet a wastewater discharge standard for ethanolamine newly adopted as a pH control agent, of whose corrosion inhibition effect was proven. The ethanolamine used as a pH control agent has a chemical formula NH2CH2CH2OH, consisting of carbon, hydrogen, oxygen and nitrogen. If the ethanolamine exists in wastewater, it causes an increase in biological oxygen demand (BOD), biochemical oxygen demand (COD), and nitrogen concentration whose values are defined in the environmental discharge standard. Therefore, the ethanolamine-containing wastewater must be treated to meet the environmental discharge standard before being discharged.
Therefore, the ethanolamine-containing wastewater discharged from a nuclear power plant or thermal power station needs to be treated in compliance with the environmental discharge standard.